WASHINGTON (AP) -- Authorities say suspicious envelopes have been found at two more District of Columbia schools a day after nearly 30 other schools received letters containing a white, powdery substance.

D.C. police spokeswoman Officer Tisha Gant says the envelopes were found at the Prospect Learning Center in northeast, and Bancroft Elementary School in northwest early Friday morning. Gant says both envelopes have been cleared of any hazardous materials.

Gant says she didn't know if the envelopes were related to the 29 letters containing a white, powdery substance that were delivered to D.C. schools Thursday. Officials say those 29 letters are similar to others mailed to schools elsewhere in the United States over the last several weeks.